One of the challenges of implementing free-space quantum key distribution (QKD) systems working in daylight is to remove unwanted background noise photons from sunlight. Elaborate elimination of background photons in the spectral, temporal, and spatial domains is an indispensable requirement to decrease the quantum bit error rate (QBER), which guarantees the security of the systems. However, quantitative effects of different filtering techniques and performance optimization in terms of the secure key rate have not been investigated. In this study, we quantitatively analyze how the performance of the QBER and the key rates changes for different combinations of filtering techniques in a free-space BB84 QKD system in daylight. Moreover, we optimize the conditions of filtering techniques in order to obtain the maximum secure key rate.

中文翻译：

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实验过滤对自由空间量子密钥分布的日光操作的影响。

实施在白天工作的自由空间量子密钥分发（QKD）系统的挑战之一是从阳光中去除不需要的背景噪声光子。在光谱，时域和空间域中精心消除背景光子是降低量子误码率（QBER）的必不可少的要求，这保证了系统的安全性。但是，尚未研究不同过滤技术的量化效果以及就安全密钥率而言的性能优化。在这项研究中，我们定量分析了自由空间BB84 QKD系统在日光下QBER的性能和关键速率对于不同滤波技术组合的变化。此外，我们优化了过滤技术的条件，以获得最大的安全密钥率。